Electric pump

ABSTRACT

An electric pump may comprise a motor, an impeller driven by the motor, and a casing comprising a pump chamber that accommodates the impeller. The motor and the pump chamber may be disposed along a rotational axis of the impeller. The casing may comprise an intake port extending in a direction parallel to the rotational axis of the impeller and a discharge port extending in a direction perpendicular to the rotational axis of the impeller. The motor may have an oblong cross section that is perpendicular to the rotational axis of the impeller.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2011-024298 filed on Feb. 7, 2011 and Japanese Patent Application No. 2012-21583 filed on Feb. 3, 2012, the contents of which are hereby incorporated by reference into the present application.

TECHNICAL FIELD

The present teachings relate to an electric pump.

DESCRIPTION OF RELATED ART

As electric pump that has a motor and a pump driven by the motor is known. In this type of electric pump, an impeller accommodated in a pump chamber is driven to rotate by a motor. The pump chamber and the motor are disposed along a rotational axis of the impeller (referred to as “rotational axis” hereinafter) so that an output of the motor is transmitted directly to the impeller. Since this type of electric pump is usually installed in a limited space, various techniques have conventionally been developed in order to downsize the electric motor. For example, an electric pump described in Japanese Patent Application Publication No. 2008-29113 achieves its downsizing by providing a motor thereof with a stator core without a coil end so that the motor can be shortened in a direction of the rotational axis of an impeller.

BRIEF SUMMARY OF INVENTION

The technology described in Japanese Patent Application Publication No. 2008-29113 downsize the electric pump by reducing the length of the motor in the direction of the rotational axis, and therefore cannot adequately improve the ability to mount the electric pump, depending on the installation environment. For example, when installing an electric pump 100 in a space S between an object A and an object B (i.e., a space limited in an x-direction only), as shown in FIG. 14A, installing the electric pump 100 in a manner that a rotational axis C thereof becomes parallel to a y-direction merely reduces the length of the electric pump 100 in a direction of its rotational axis (i.e., the y-direction); therefore, such installation does not improve the ability to mount the electric pump 100. On the other hand, when installing the electric pump 100 in a manner that the rotational axis C thereof becomes parallel to the x-direction, as shown in FIG. 14B, an intake pipe connected to a intake port 102 for sucking fluid into a pump chamber needs to be bent at a steep angle because the intake port 102 also extends parallel to the x-direction. In other words, because the direction for downsizing the electric pump matches the direction in which the intake port extends, a problem occurs in the intake pipe. Therefore, the technology described in Japanese Patent Application Publication No. 2008-29113 cannot adequately improve the ability to mount the electric pump in the environments illustrated in FIGS. 14A and 14B.

If the intake port can be formed to extend in a direction perpendicular to the rotational axis, even the technology described in Japanese Patent Application Publication No. 2008-29113 can improve the ability to mount the electric pump. However, in this type of electric pump, the pressure of the fluid in the pump chamber is increased by the centrifugal force of the rotating impeller. For this reason, forming the intake port to extend in the direction perpendicular to the rotational axis makes it difficult to suck the fluid into the pump chamber. Therefore, in reality, it is difficult to form the intake port to extend in the direction perpendicular to the rotational axis.

It is an object of the present teachings to provide a technology that is capable of improving the ability to mount an electric pump even when the electric pump is installed in the environments shown in FIG. 14.

An electric pump disclosed in the present specification comprises a motor, an impeller that is driven to rotate by the motor, and a pump chamber accommodating the impeller. The motor and the pump chamber are disposed along a rotational axis of the impeller. This electric pump further comprises an intake port for sucking fluid into the pump chamber, and a discharge port for discharging the fluid of the pump chamber. The intake port extends in a direction parallel to the rotational axis, while the discharge port extends in a direction perpendicular to the rotational axis. A cross section of the motor that is perpendicular to the rotational axis is oblong.

In this electric pump, the cross section of the motor that is perpendicular to the rotational axis is oblong. Therefore, when a direction of the rotational axis of the electric pump is taken as a height direction, either the width or the depth of the motor is made shorter. In other words, the size of the motor is reduced in a direction perpendicular to the rotational axis. Furthermore, because the intake port extends in a direction parallel to the rotational axis, the direction in which the motor is reduced does not match the direction of the intake port. For this reason, installing the electric pump in the environments shown in FIG. 14 does not cause the problem where the intake pipe is bent at a steep angle, and this electric pump can improve the ability to mount the electric pump.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic cross-sectional diagram of an electric pump of Embodiment 1.

FIG. 2 is a cross-sectional diagram taken along line II-II shown in FIG. 1.

FIG. 3 is a cross-sectional diagram taken along line III-III shown in FIG. 1.

FIG. 4 is a diagram showing a schematic configuration of a pump chamber of an electric pump of Modification 1.

FIG. 5 is a diagram showing a schematic configuration of a motor of the electric pump of Modification 1.

FIG. 6 is a diagram showing a schematic configuration of a pump chamber of an electric pump of Modification 2.

FIG. 7 is a diagram showing a schematic configuration of a motor of the electric pump of Modification 2.

FIG. 8 is a diagram showing a schematic configuration of a pump chamber of an electric pump of Modification 3.

FIG. 9 is a diagram showing a schematic configuration of a pump chamber of an electric pump of Modification 4.

FIG. 10 is a diagram showing a schematic configuration of a pump chamber of an electric pump of Modification 5.

FIG. 11 is a diagram showing a modification of the motor.

FIG. 12 is a diagram showing another modification of the motor.

FIG. 13 is a diagram schematically showing a state in which the electric pump of the embodiment is mounted in an engine room of an automobile.

FIGS. 14A and 14B are diagrams for illustrating problems of the electric pump of the conventional technology.

FIG. 15 is a diagram showing a modification of the motor.

FIG. 16 is a diagram showing another modification of the motor.

FIG. 17 is a diagram showing another modification of the motor.

FIG. 18 is a diagram showing another modification of the motor.

FIG. 19 is a diagram showing another modification of the motor.

FIG. 20 is a diagram showing another modification of the motor.

FIG. 21 is a diagram showing another modification of the motor.

FIG. 22 is a schematic cross-sectional diagram of an electric pump of another embodiment.

DETAILED DESCRIPTION OF INVENTION

In an electric pump disclosed in the present specification, a cross section of a pump chamber that is perpendicular to the rotational axis may have an outline such that a distance between the outline and the rotational axis of the impeller changes gradually in a circumferential direction. The distance between the outline and the rotational axis of the impeller may be maximum at a point corresponding to the position of a discharge port. In this case, the cross section of a motor that is perpendicular to the rotational axis may have a first outside dimension in a first direction and a second outside dimension in a second direction perpendicular to the first direction. It is preferred that a length of the first outside dimension is longer than a length of the second outside dimension and that the discharge port extends in a direction parallel to the second direction. When the pump chamber projects from the motor in the direction perpendicular to the rotational axis when the electric pump is viewed along the rotational axis, the configuration described above can reduce the distance in which the pump chamber projects from the motor.

Moreover, the motor may comprise a rotor connected to the impeller and a stator disposed around the rotor. When the motor is viewed along the rotational axis, a position of a center of the rotor may be different from a position of a center of the stator. Because the rotor and the impeller are connected to each other, the center (rotational axis) of the rotor matches the center (rotational axis) of the impeller. Thus, the position of the pump chamber in relation to the stator can be shifted by making the center of the rotor different from the center of the stator. As a result, when the pump chamber projects from the motor in the direction perpendicular to the rotational axis when the electric pump is viewed along the rotational axis, the position, the direction and the distance in which the pump chamber projects from the motor can be adjusted.

The electric pump disclosed in the present specification may further comprise a motor driving circuit that drives the motor, and a circuit chamber for accommodating the motor driving circuit. In this case, the pump chamber, the motor and the circuit chamber may be disposed along the rotational axis, and the motor may be disposed between the pump chamber and the circuit chamber. With such a configuration, the pump chamber, the motor and the circuit chamber are disposed along the rotational axis. As a result, the electric pump can be prevented from increasing its size in a direction perpendicular to the rotational axis. The motor driving circuit may have a circuit substrate with circuit elements, and the circuit substrate may extend in a direction parallel to the rotational axis or in a direction perpendicular to the rotational axis.

The electric pump disclosed in the present specification may further comprise an attaching surface that is used for attaching the electric pump to an external device. The discharge port may protrude from the attaching surface in a direction perpendicular to the attaching surface. According to this configuration, the discharge port of the electric pump may be inserted and coupled directly to an intake port of the external device, thereby reducing the number of pipes connecting the electric pump and the external device.

Embodiment 1

An electric pump 10 of Embodiment 1 is installed in an engine room of an automobile and used for circulating cooling water for cooling an engine, an inverter, and the like. As shown in FIG. 1, the electric pump 10 has a casing 12, a fixed shaft 24, a rotator 23, and a stator 30.

Three spaces of a pump chamber 14, a motor chamber 16 and a circuit chamber 18 are formed inside the casing 12. The pump chamber 14 is formed in an upper part of the casing 12. An intake port 20 and a discharge port 22 (see FIG. 2) that are formed in the casing 12 are connected to the pump chamber 14. The intake port 20 is connected to an upper end of the pump chamber 14. The intake port 20 extends in a direction in which a rotational axis of the rotator 23 extends (i.e., a z-direction). As shown in FIG. 2, the discharge port 22 is connected to an outer circumference of the pump chamber 14. The discharge port 22 extends in a tangential direction of the outer circumference of the pump chamber 14 (i.e., an x-direction). An outer shape of the pump chamber 14 (an outer shape in an x-y planar surface) is shaped in a manner that a distance between the outer shape and the rotational axis of the rotator 23 changes gradually in a circumferential direction. Specifically, the distance between the outer shape and the rotational axis of the rotator 23 gradually increases from a P point (a point adjacent to the discharge port 22) in clockwise direction, and becomes maximum at the position of the discharge port 22. In other words, the pump chamber 14 has the same shape as a centrifugal pump.

The motor chamber 16 is formed below the pump chamber 14. An upper end of the motor chamber 16 is connected to a lower end of the pump chamber 14, and the motor chamber 16 and the pump chamber 14 are communicated with each other. A lower end of the fixed shaft 24 is fixed to a bottom surface of the motor chamber 16. The fixed shaft 24 extends upward from the bottom surface of the motor chamber 16, inside the motor chamber 16, and has a tip end reaching the inside of the pump chamber 14. The circuit chamber 18 is formed below the motor chamber 16 and separated from the pump chamber 14 and the motor chamber 16. The circuit chamber 18 accommodates a motor driving circuit 37.

The rotator 23 is attached rotatably to the fixed shaft 24. The rotator 23 has an impeller 26 and a rotor 28. An upper surface of the impeller 26 is tilted downward toward an outer circumferential end of the impeller 26. As shown in FIG. 2, when the impeller 26 is viewed in a planar view (from the top of FIG. 1), the impeller 26 has a circular shape. A plurality of blades is formed at regular intervals in the upper surface of the impeller 26. Each of the blades extends in a radial direction of the impeller 26. The cylindrical rotor 28 is formed below the impeller 26. The rotor 28, made of a magnetic material, is subjected to a predetermined magnetizing process. The rotor 28 is accommodated in the motor chamber 16. The impeller 26 and the rotor 28 are molded integrally. Therefore, when the rotor 28 rotates, the impeller 26 rotates integrally with the rotor 28.

Within the casing 12 that forms the motor chamber 16, the stator 30 is disposed so as to face the rotor 28. As shown in FIG. 3, the stator 30 has a pair of cores 32, 34 and coils 36. Each of the coils 36 is wound around a corresponding slot of slots 32 a to 32 c and 34 a to 34 c of the cores 32 and 34. The cores 32, 34 are disposed symmetrically with the rotor 28 therebetween. Tip ends of the slots 32 a to 32 c and 34 a to 34 c of the cores 32 and 34 face an outer circumferential surface of the rotor 28. The coils 36 are connected to the motor driving circuit 37 by wires 38 a (see FIG. 1). The rotor 28 and the impeller 26 are rotated by power that is supplied from the motor driving circuit 37 to the coils 36. In the present embodiment, a motor is configured by the rotor 28 and the stator 30.

As is clear in FIG. 3, the cores 32,34 are made shorter in an x-direction and longer in a y-direction. In a section where the motor chamber 16 is formed, an outer shape of a cross section of the casing 12 that is perpendicular to the rotational axis is oblong. Specifically, the outer shape is a rectangular shape with a short side 12 a and a long side 12 b. Furthermore, as is clear in FIG. 2, when the pump chamber 14 is viewed along the rotational axis of the rotator 23, the pump chamber 14 is positioned within a range corresponding to the outer shape of the section within the casing 12 where the motor chamber 16 is formed. In other words, in the position where the motor chamber 16 is formed, the pump chamber 14 does not project from the casing 12.

Note that, in the present embodiment, a surface on the long side 12 b of the casing 12 configures an attaching surface that is used for attaching the electric pump to an external device. As is clear in FIG. 2, the discharge port 22 protrudes from the attaching surface of the casing 12 in a direction of the short side 12 a (i.e., the x-direction).

The motor driving circuit 37 that supplies power to the stator 30 is accommodated in the circuit chamber 18 of the casing 12. The motor driving circuit 37 is configured by a circuit substrate 38 and circuit elements 39 mounted on surfaces 38 c, 38 d of the circuit substrate 38. The motor driving circuit 37 is connected to an external power source (e.g., a battery mounted in a vehicle), not shown, by a wire 38 b. The motor driving circuit 37 converts power supplied from the external power source, into power to be supplied to the coil 36, and supplies the converted power to the coil 36.

Note that the surfaces 38 c, 38 d of the circuit substrate 38 are formed parallel to the rotational axis of the rotator 23. Therefore, compared to a case where the surfaces 38 c, 38 d of the circuit substrate 38 are formed perpendicular to the rotational axis of the rotator 23, the outer shape of the cross section of the casing 12 that is perpendicular to the rotational axis can be prevented from increasing in the position where the circuit chamber 18 is formed. In the present embodiment, the outer shape of the cross section of the casing 12 that is perpendicular to the rotational axis in the position where the circuit chamber 18 is formed is same in the position where the motor chamber 16 is formed.

Next, operations of the electric pump 10 are described. Once the power is supplied to the stator 30, the rotator 23 rotates around the fixed shall 24. As a result, the impeller 26 is rotated, and cooling water is sucked by the intake port 20 into the pump chamber 14. The pressure of the fluid sucked into the pump chamber 14 increases as the impeller 26 rotates, and then discharged from the discharge port 22 to the outside of the casing 12.

The electric pump 10 described above is installed between a radiator 54 and an inverter device 51 within an engine room of an automobile 56, as shown in FIG. 13. Specifically, the electric pump 10 is attached to the inverter device 51 such that the attaching surface of the electric pump 10 (i.e., the surface on the long side 12 b of the casing 12) abuts against the inverter device 51. Therefore, a surface on the short side of the electric pump 10 (i.e., the surface on the short side 12 a) matches a direction from the radiator 54 to the inverter device 51 (i.e., the x-direction in the diagram) and can increase the distance between the radiator 54 and the electric pump 10 (L-d). As a result, a collision safety space can be secured adequately between the radiator 54 and the electric pump 10.

Moreover, in a state in which the electric pump 10 is attached to the inverter device 51, the discharge port 22 of the electric pump 10 is inserted into an entrance of a cooling flow path 50 for cooling a driving circuit 52 of the inverter device 51. In other words, the discharge port 22 of the electric pump 10 is connected directly to the cooling flow path 50 of the inverter device 51. For this reason, a pipe or the like for connecting the electric pump 10 to the inverter device 51 is not required. On the other hand, a cooling water pipe is connected to the intake port 20 of the electric pump 10. Because the direction in which the intake port 20 extends is perpendicular to the direction from the radiator 54 to the inverter device 51 (i.e., the x-direction in the diagram), the cooling water pipe connected to the intake port 20 does not have to be bent at a steep angle.

As is clear from the description above, by forming the stator 30 (the casing 12 of the motor) into an oblong shape, the electric pump 10 can be downsized in the direction of the electric pump 10 that is perpendicular to the rotational axis. Therefore, the ability to mount the electric pump 10 in the space between the radiator 54 and the inverter device 51 can be improved. In addition, the space for installing the electric pump 10 can be conserved, improving the degree of freedom in laying out other devices. On the other hand, because the direction in which the intake port 20 of the electric pump 10 extends is perpendicular to the direction of downsizing the electric pump 10, the cooling pipe connected to the intake port 20 does not have to be bent at a steep angle.

Specific embodiment of the present teachings is described above, but this merely illustrates some representative possibilities for utilizing the present teachings and does not restrict the claims thereof. The subject matter set forth in the claims includes variations and modifications of the specific examples set forth above.

For example, in the embodiment described above, when the electric pump 10 is viewed along the rotational axis, the pump chamber 14 is formed so as not to project to the outside of the casing 12 (referred to as “casing of the motor,” hereinafter) at the position where the motor (28, 30) is provided. However, the pump chamber 14 may be formed so as to project to the outside of the casing 12 of the motor, as shown in FIGS. 4 and 5. This configuration can increase the capacity of the pump chamber 14 and improve its pumping ability.

In this case, the direction in which the discharge port 22 extends may be oriented in any direction as long as it matches the tangential direction of the outer circumference of the pump chamber 14. However, it is preferred that the discharge post 22 extends in a direction perpendicular to the long side 12 b of the casing 12 (i.e., parallel to the short side 12 a), as shown in FIG. 4. In other words, the distance between the pump chamber 14 and the rotational axis of the rotator becomes the longest at the position of the discharge port 22. Thus, by disposing the discharge port 22 in the direction perpendicular to the long side 12 b, the section where the distance between the pump chamber and the rotational axis becomes the longest is located within the range of the short side 12 a of the casing 12. As a result, the distance in which the pump chamber 14 projects from the casing 12 can be reduced to the minimum.

It should be noted that, in the examples shown in FIGS. 4 and 5, the rotational axis of the rotor 28 (i.e., the rotational axis of the impeller 26) matches the center of the cores 32, 34. Here, the center of the cores 32, 34 means a central point between a section of the central slot 32 c where the coil 36 is wound and a section of the central slot 34 c where the coil 36 is wound, in a cross section perpendicular to the rotational axis of the rotor 28. On the other hand, the outer shape of the pump chamber 14 is the shape of a centrifugal pump in which the distance between the pump chamber 14 and the rotational axis of the impeller 26 changes gradually. Therefore, when the electric pump 10 is viewed along the rotational axis, the pump chamber 14 projects to the outside of the casing 12 of the motor on an upper side of the casing 12, and is located inside the casing 12 on a lower side (see FIG. 4).

However, the pump chamber 14 can be prevented from projecting from the casing 12 of the motor, when viewing the electric pump along a rotational axis Cr of the rotor 28, by making the central axis Cr different from a center Cs of the cores 32, 34, as shown in FIGS. 6 and 7. In other words, in the examples shown in FIGS. 6 and 7, tip end teeth parts of the slots 32 a to 32 c and 34 a to 34 c are deformed in the x-direction of FIG. 7. The rotor 28 is positioned in the middle of the tip end teeth parts of the slots 32 a to 32 c and 34 a to 34 c. Consequently, the rotational axis Cr of the rotor 28 is shifted in the x-direction of FIG. 7. On the other hand, the sections of the slots 32 c, 34 c where the coils 36 are wound are not deformed in the x-direction, so the position of the center Cs of the cores 32, 34 is not changed. Therefore, the rotational axis Cr of the rotor 21 is shifted in the x-direction with respect to the center Cs of the cores 32, 34. Consequently, the pump chamber 14 is shifted in the x-direction with respect to the center Cs of the cores 32, 34, preventing the pump chamber 14 from projecting from the casing 12 of the motor when the electric pump is viewed along the rotational axis Cr. According to this electric pump, downsizing of the electric pump can be further realized, while increasing the capacity of the pump chamber.

Note that the direction and the distance in which the rotational axis Cr of the rotor 28 is shifted with respect to the center Cs of the cores 32, 34 can be set appropriately in accordance with the positional relationship between the electric pump and a space or an external device in which the electric pump is installed (e.g., the inverter device 51 or the radiator 54 in Embodiment 1). For instance, as in the example shown in FIG. 8, the position of the rotational axis Cr of the rotor 28 may be shifted in a manner that the pump chamber 14 projects evenly in a vertical direction of the casing 12 of the motor. Alternately, as in the example shown in FIG. 9, the position of the rotational axis Cr of the rotor 28 may be shifted in a manner that the pump chamber 14 projects only upward from the casing 12 of the motor.

In addition, the shape of the discharge port 22 is not limited to the shape described in the embodiment. For example, as shown in FIG. 10, a discharge port 38 may curve along the outer circumference of the pump chamber 14 and be pulled out in the x-direction. In such an aspect, the discharge port 38 can be positioned closer to the center of the electric pump.

Moreover, the configuration of the motor is not limited to the configuration described in each of the embodiments. For example, as shown in FIG. 11, a core 40 for coupling slots 44 disposed above and below the rotor 28 to each other with coupling pieces 42 a, 42 b may be used. The positional accuracy of each slot 44 can be increased by using the core 40. Alternatively, as with the embodiments described above, a pair of cores 46 may be disposed above and below the rotor 28, as shown in FIG. 12.

Furthermore, in each of the embodiments described above, the outer shape of the cross section of the casing 12 of the motor that is perpendicular to the rotational axis is a rectangular shape; however, the outer shape is not limited to the one described in the embodiments and can be any shape as long as it is oblong. For example, the outer shape of the cross section may be an oval shape or a shape obtained by bending four sides configuring a rectangular. Furthermore, the outer shape of the cross section of the casing 12 of the motor may have any one of shapes shown in FIGS. 15 to 21. Specifically, as shown in FIGS. 15 and 16, the outer shape of the cross section may have a rectangular shape with curved corner portions. As shown in FIG. 17, the outer shape of the cross section may have a rectangular shape whose comers are planed off. As shown in FIG. 18, the outer shape of the cross section may have a trapezoidal shape with an upper base that is shorter than a lower base. As shown in FIG. 19, the outer shape of the cross section may have a rectangular shape with a short side which is shorter than a diameter of a rotor 28. As shown in FIG. 20, the outer shape of the cross section may have a hexagonal shape. As shown in FIG. 21, the outer shape of the cross section may have an upper side and a lower side that diagonally extend relative to a horizontal direction. As is clear from FIGS. 15 to 21, each of the outer shape of the cross sections shown in FIGS. 5 to 21 has an oblong shape, and a length (a) of horizontal dimension is longer than a length (b) of the vertical dimension. Further, it is preferred that a ratio of the length (a) to the length (b) is more than or equal to 1.3 in order to increase a volume of the rotor as well as a volume of the stator.

Further, in the Embodiment 1 described above, the surfaces of the circuit substrate are formed parallel to the rotational axis of the rotator; however, as shown in FIG. 22, surfaces of the circuit substrate 38 may be formed perpendicular to the rotational axis of the rotator. 

1. An electric pump comprising: a motor; an impeller driven by the motor; and a casing comprising a pump chamber that accommodates the impeller, wherein the motor and the pump chamber are disposed along a rotational axis of the impeller, the casing comprises an intake port extending in a direction parallel to the rotational axis of the impeller and a discharge port extending in a direction perpendicular to the rotational axis of the impeller, and the motor has an oblong cross section that is perpendicular to the rotational axis of the impeller.
 2. The electric pump as in claim 1, wherein the pump chamber has a cross section that is perpendicular to the rotational axis of the impeller, the cross section of the pump chamber has an outline such that a distance from the outline to the rotational axis of the impeller changes in a circumferential direction, the distance becoming maximum at a point corresponding to the discharge port, the oblong cross section of the motor has a first outside dimension in a first direction and a second outside dimension in a second direction perpendicular to the first direction, a length of the first outside dimension is longer than a length of the second outside dimension, and the discharge port extends in a direction parallel to the second direction.
 3. The electric pump as in claim 2, wherein the motor comprises a rotor connected to the impeller and a stator disposed around the rotor, and when the motor is viewed along the rotational axis of the impeller, a position of a center of the rotor is different from a position of a center of the stator.
 4. The electric pump as in claim 3, further comprising a motor driving circuit that drives the motor, wherein the casing further comprises a circuit chamber that accommodates the motor driving circuit, the pump chamber, the motor and the circuit chamber are disposed along the rotational axis of the impeller, the motor is disposed between the pump chamber and the circuit chamber, the motor driving circuit comprises a circuit substrate with circuit elements, and the circuit substrate is parallel or perpendicular to the rotational axis of the impeller.
 5. The electric pump as in claim 4, wherein the casing further comprises an outer surface with an attaching surface part adapted to be attached to an external device, and the discharge port projects from the attaching surface part in a direction perpendicular to the attaching surface part.
 6. The electric pump as in claim 1, further comprising a motor driving circuit that drives the motor, wherein the casing further comprises a circuit chamber that accommodates the motor driving circuit, the pump chamber, the motor and the circuit chamber are disposed along the rotational axis of the impeller, the motor is disposed between the pump chamber and the circuit chamber, the motor driving circuit comprises a circuit substrate with circuit elements, and the circuit substrate is parallel or perpendicular to the rotational axis of the impeller.
 7. The electric pump as in claim 6, wherein the pump chamber has a cross section that is perpendicular to the rotational axis of the impeller, the cross section of the pump chamber has an outline such that a distance from the outline to the rotational axis of the impeller changes in a circumferential direction, the distance becoming maximum at a point corresponding to the discharge port, the oblong cross section of the motor has a rectangular shape comprising a first side extending in a first direction, and a second side extending in a second direction perpendicular to the first direction, a length of the first side is longer than a length of the second side, and the discharge port extends in a direction parallel to the second direction.
 8. The electric pump as in claim 1, wherein the casing further comprises an outer surface with an attaching surface part adapted to be attached to an external device, and the discharge port projects from the attaching surface part in a direction perpendicular to the attaching surface part.
 9. The electric pump as in claim 8, wherein the pump chamber has a cross section that is perpendicular to the rotational axis of the impeller, the cross section of the pump chamber has an outline such that a distance from the outline to the rotational axis of the impeller changes in a circumferential direction, the distance becoming maximum at a point corresponding to the discharge port, the oblong cross section of the motor has a rectangular shape comprising a first side extending in a first direction and a second side extending in a second direction perpendicular to the first direction, a length of the first side is longer than a length of the second side, and the discharge port extends in a direction parallel to the second direction.
 10. The electric pump as in claim 9, wherein the motor comprises a rotor connected to the impeller and a stator disposed around the rotor, and when the motor is viewed along the rotational axis of the impeller, a position of a center of the rotor is different from a position of a center of the stator.
 11. An electric pump comprising: a motor; an impeller driven by the motor; and a casing comprising a pump chamber that accommodates the impeller, wherein the motor and the pump chamber are disposed along a rotational axis of the impeller, the casing comprises an intake port extending in a direction parallel to the rotational axis of the impeller and a discharge port extending in a direction perpendicular to the rotational axis of the impeller, and the motor has a rectangular cross section that is perpendicular to the rotational axis of the impeller, the cross section of the motor comprising a first side extending in a first direction and a second side extending in a second direction perpendicular to the first direction.
 12. The electric pump as in claim 11, wherein the pump chamber has a cross section that is perpendicular to the rotational axis of the impeller, the cross section of the pump chamber has an outline such that a distance from the outline to the rotational axis of the impeller changes in a circumferential direction, the distance becoming maximum at a point corresponding to the discharge port, a length of the first side is longer than a length of the second side, and the discharge port extends in a direction parallel to the second direction.
 13. The electric pump as in claim 12, wherein the motor comprises a rotor connected to the impeller and a stator disposed around the rotor, and when the motor is viewed along the rotational axis of she impeller, a position of a center of the rotor is different from a position of a center of the stator.
 14. The electric pump as in claim 13, further comprising a motor driving circuit that drives the motor, wherein the casing further comprises a circuit chamber that accommodates the motor driving circuit, the pump chamber, the motor and the circuit chamber arc disposed along the rotational axis of the impeller, the motor is disposed between the pump chamber and the circuit chamber, the motor driving circuit comprises a circuit substrate with circuit elements, and the circuit substrate is parallel or perpendicular to the rotational axis of the impeller.
 15. The electric pump as in claim 14, wherein the casing further comprises an outer surface with an attaching surface part adapted to be attached to an external device, and the discharge port projects from the attaching surface part in a direction perpendicular to the attaching surface part. 